This invention relates to emitters for drip irrigation systems, and more particularly to pressure compensating emitters.
Drip or trickle irrigation systems have come into widespread use, particularly for arid, semi-arid and other environments in which irrigation is employed, because it has been shown that for various crops and plant life, such systems can provide either a substantial savings in water usage, increased growth rate, or both. Numerous valve or emitter designs have been attempted or adopted, and most are based upon the principle of reducing the flow volume to a selected low rate of flow by introducing long or multiple constricted paths through which the water must pass. These emitters are generally made wholly or in substantial part of plastic, are bulky and subject to damage, and while some may be removed for cleaning, this in itself is usually a time consuming and tedious procedure. In addition to these disadvantages, present systems are inordinately subject to clogging unless filtration is used, to the extent that most large scale systems are designed on the inherent assumption that filtration is required. Additionally, most commercial emitters today are inherently static devices with respect to the pressure range in which they will operate satisfactorily. In large scale agri-business today, however, it is common to desire to use long pipe lengths (e.g. 1000 ft.), and to be required to follow a variable land contour. The pressure differences arising from line lengths in excess of about 300 ft. and changes in elevation can each cause the static emitters to provide widely and unacceptably varying rates of flow. To overcome these variations it is necessary to use both pressure regulating equipment and extensive header installations.
Attempts have been made to confront individual ones of the different problems separately. For example, a number of designs of pressure compensating emitters have been patented, typically derived from the designs of pressure regulators utilized in large conventional piping systems. Other attempts have been made at providing flushing features, and at minimizing the problems of emitter clogging. It is clear, however, that no one has yet conceived an emitter which is capable of satisfying all these requirements, and at substantially lower cost than existing emitters, while also being so small in size and so rugged in structure that it can be utilized with automatic handling equipment. Most present emitters are relatively bulky (e.g. 2" or more in one dimension), or when configured for in-line mounting cannot readily be replaced. Further, no emitters are known, as far as can be ascertained, that can provide low feed rates (e.g. 1 quart per hour) at pressures normally available in service.